Cross off Las Vegas from your list right now. Very limited flight options and very full flights. Los Angeles has the most flights to Honolulu. United and American have the most departures out of LAX to HNL. Hawaiian has two daily departures to HNL.

All things being equal, I'd probably try LAX. But, make sure to get backup passes. DO NOT limit yourself to just one airline...or one city routing for that matter. If I were you, get round trip passes on Hawaiian, American, and United. And, buy some extra one-way passes from HNL as backups to get back to the mainland. You can always refund the passes you don't use. But, there is no Southwest ticket counter in the islands to help you if you get in a bind.